EENG 755 Computer Networks

Ø Michael Hutt, Adjunct Professor l  Engineering and Computing Sciences

Ø http://huttsystems.com/nyit Ø mhutt@nyit.edu Ø @mfhutt

Textbook/References Ø  Stallings, William, “Data and Computer Communications,

10/E”, Prentice Hall, 2014. ISBN-10: 0133506487 • ISBN-13: 9780133506488

Ø  Stevens, W. Richard, “TCP/IP Illustrated Volume 1”, Addison Wesley, 1994. ISBN:0-201-63346-9

Ø  Stevens, W. Richard, “UNIX Network Programming

Volume 1”, 2nd Edition, Prentice Hall, 1998. ISBN:0-13-490012-X

Ø  Tanenbaum, A., “Computer Networks, 5th Edition”, Prentice Hall, 2011

Logistics

Ø 15 Classes (no class on 3/6)

Ø No more than 2 absences

Ø Assignments, Midterm Exam, Final Project

Supplemental Material

Ø Virtual Box Ø Ubuntu Ø nmap Ø netcat Ø Wireshark or tcpdump Ø Mininet (http://mininet.org/)

Data Communications, Data Networks, and the Internet

LECTURE 1

“The fundamental problem of communication is that of reproducing at one point either exactly or approximately a message selected at another point”

- The Mathematical Theory of Communication, Claude Shannon

Technological Advancement Driving Forces

Figure 1.1 Average Downstream Traffic per Internet Subscriber

20

January 2010

Aver

age

data

rat

e pe

r sub

scri

ber (

kbps

)

January 2011

40

60

80

100

Other protocols120

140

160

Web browsing

Peer-to-peer

Streaming media

Notable Trends Trend toward faster and cheaper, in both computing and communication • More powerful computers supporting more

demanding applications • The increasing use of optical fiber and high-

speed wireless has brought transmission prices down and greatly increased capacity

Today’s networks are more “intelligent” • Differing levels of quality of service (QoS) • Variety of customizable services in the areas

of network management and security

The Internet, the Web, and associated applications have emerged as dominant features for both business and personal network landscapes •  “Everything over IP” •  Intranets and extranets are being used to

isolate proprietary information

Mobility •  iPhone, Droid, and iPad have become

drivers of the evolution of business networks and their use

• Enterprise applications are now routinely delivered on mobile devices

• Cloud computing is being embraced

1995100 Mbps

1 Gbps

10 Gbps

100 Gbps

1 Tbps

2000 2005 2010 2015 2020

Ethernet data rate standard

Figure 1.2 Past and Projected Growth in Ethernet DataRate Demand Compared to Existing Ethernet Data Rates

Core Networking/Service provider/WANDoubling 18 months ≈

≈

Enterprise/server/LANDoubling 24 months

Changes in Networking Technology

* Emergence of high-speed LANs

* Digital electronics

* Corporate WAN needs

Emergence of High-Speed LANs Ø  Personal computers and microcomputer

workstations have become an essential tool for office workers

Ø  Examples of requirements that call for higher-speed LANs: l  Centralized server farms l  Power workgroups l  High-speed local backbone

Two significant

trends altered the

requirements of the LAN

Explosive growth of speed and

computing power of personal computers

LANs have been recognized as a

viable and essential

computing platform

Corporate Wide Area Networking Needs

Changes in corporate data traffic patterns are driving the creation of high-speed WANs

Growing use of telecommuting

Nature of the application structure has changed

Intranet computing

More reliance on personal computers, workstations, and servers

More data-intensive applications

Most organizations require access to the Internet

Traffic patterns have become more unpredictable

Average traffic load has risen

More data is transported off premises and into the wide area

Digital Electronics

Ø The rapid conversion of consumer electronics to digital technology is having an impact on both the Internet and corporate intranets l  Image and video traffic carried by networks is

dramatically increasing •  Because of their huge storage capacity digital versatile

disks (DVDs) are being incorporated into Web sites •  Digital camcorders have made it easier to make digital

video files to be placed on corporate and Internet Web sites

Convergence Ø  The merger of previously

distinct telephony and information technologies and markets

l  Involves: •  Moving voice into a

data infrastructure •  Integrating all the voice

and data networks inside a user organization into a single data network infrastructure

•  Then extending that into the wireless arena

l  Foundation is packet-based transmission using the Internet Protocol (IP)

l  Increases the function and scope of both the infrastructure and the application base

Applications

These are seen by the end users

Enterprise services

Services the information network supplies to support applications

Infrastructure

Communication links available to the enterprise

Layers:

Source Trans-mitter

Trans-missionSystem

Receiver Destination

SourceSystem Destination System

(a) General block diagram

(b) Example

Figure 1.3 Simplified Communications Model

ServerModemModemPublic Telephone Network

Workstation

Table 1.1 Communications Tasks

Source Trans-mitter

Trans-missionSystem

Receiver Destination

Figure 1.4 Simplified Data Communications Model

Text Text

Digital bitstream

Analogsignal

Digital bitstream

Analogsignal

1 2 3 4 5 6Input

informationm

Input datag(t)

Transmittedsignal

s(t)

Receivedsignal

r(t)

Output datag'(t)

Outputinformation

m'

The basic building block of any communications facility is the transmission line

The business manager is concerned with a facility providing the required capacity, with acceptable reliability, at minimum cost

Capacity

Reliability

Cost

Transmission Line

Transmission Lines

Transmission Mediums Two mediums currently driving the evolution of data communications

transmission are:

Fiber optic transmissionsand

Wireless transmissions

Transmission Services Ø  Remain the most costly component of a

communications budget Ø  Two major approaches to greater efficiency:

Networks Ø  It is estimated that by 2016 there will be

over 20 billion fixed and mobile networked devices l  This affects traffic volume in a number of

ways: •  It enables a user to be continuously consuming

network capacity •  Capacity can be consumed on multiple devices

simultaneously •  Different broadband devices enable different

applications which may have greater traffic generation capability

Networking

Voice Data

Image Video

Advances in technology have led to greatly increased capacity and the concept of integration, allowing equipment and networks to work simultaneously

Wide Area Networks (WANs)

Ø Span a large geographical area

Ø Require the crossing of public right-of-ways

Ø Rely in part on common carrier circuits

Ø Typically consist of a number of interconnected switching nodes

Wide Area Networks Alternative technologies used include:

l  Circuit switching l  Packet switching l  Frame relay l  Asynchronous Transfer Mode (ATM)

Circuit Switching

Ø Uses a dedicated communications path Ø Connected sequence of physical links

between nodes Ø Logical channel dedicated on each link Ø Rapid transmission Ø The most common example of circuit

switching is the telephone network

Packet Switching

Ø Data are sent out in a sequence of small chunks called packets

Ø Packets are passed from node to node along a path leading from source to destination

Ø Packet-switching networks are commonly used for terminal-to-terminal computer and computer-to-computer communications

Frame Relay

Ø Developed to take advantage of high data rates and low error rates

Ø Operates at data rates of up to 2 Mbps Ø Key to achieving high data rates is to strip

out most of the overhead involved with error control

Asynchronous Transfer Mode (ATM)

Ø Referred to as cell relay Ø Culmination of developments in circuit

switching and packet switching Ø Uses fixed-length packets called cells Ø Works in range of 10s and 100s of Mbps

and in the Gbps range Ø Allows multiple channels with the data rate

on each channel dynamically set on demand

Local Area Networks (LAN)

The Internet

Ø  Internet evolved from ARPANET Ø Developed to solve the dilemma of

communicating across arbitrary, multiple, packet-switched networks

Ø Foundation is the TCP/IP protocol suite

Ethernetswitch

Ethernetswitch

Router

RouterStandaloneMainframe

Router

Router

Wide Area Network(e.g. ATM)

Local AreaNetwork

Local AreaNetwork

Wide Area Network(e.g. ATM)

Figure 1.5 Key Elements of the Internet

Informationserver

LAN PCsand workstations

Figure 1.6 Simplified View of Portion of Internet

BackboneISP

BackboneISP

RegionalISP

LANswitch

CorporateLAN

CorporateLAN

Residentialsubscribers

Server

Server

Server

ISP Webfarm

RegionalISP

Private peering

RegionalISP

open circle = NAPfilled circle = POP

Table 1.2 Internet Terminology

Ø  Central Office (CO)

l  The place where telephone companies terminate customer lines and locate switching equipment to interconnect those lines with other networks

Ø  Customer Premises Equipment (CPE)

l  Telecommunications equipment that is located on the customer’s premises

Ø  Internet Service Provider (ISP) l  A company that provides other

companies or individuals with access to, or presence on, the Internet

Ø  Network Access Point (NAP) l  One of several major Internet

interconnection points that serve to tie all the ISPs together

Ø  Network Service Provider (NSP)

l  A company that provides backbone services to an Internet service provider (ISP)

Ø  Point of Presence (POP) l  A site that has a collection of

telecommunications equipment, usually refers to ISP or telephone company sites

(Table can be found on page 27 in textbook)

Figure 1.7 A Networking Configuration

IPbackbone

ATMWAN

Enterprisenetwork

(main campus)

Ethernet LAN

Corerouter

Edge/aggregaterouter

Router Ethernetswitch

ATMswitch

Wi-Fi accesspoint

Router withfirewall

Networkingicons:

Residential Wi-Finetwork

Public cellularnetwork

Enterprisenetwork(branch)

Summary

Ø  Trends challenging data communications: l  Traffic growth l  Development of new

services l  Advances in

technology Ø  Data Transmission

and Network Capacity Requirements

Ø  Convergence

Ø  Transmission mediums l  Fiber optic l  Wireless

Ø  Network categories: l  Wide Area Networks l  Local Area Networks l  Wireless Networks

Ø  Internet l  Origin l  Key elements l  Internet architecture